The present invention relates to an electro-optical overhead wire and, more particularly, to an electro-optical overhead wire containing at least 24 light wave guides (LWG).
An electro-optical overhead wire is described in Published German Utility Patent 90 01 893 U1. This electro-optical overhead wire is made from circular cross-sectioned cable strand elements. The core is provided with at least one layer of primarily high tensile strength wires and additionally at least one layer of chiefly electrically conducting wires. At least one strand element of the overhead wire is replaced by a high quality steel tube, in which a plurality of light wave guides (LWG) are loosely placed and extend over the length of the cable (LWL tube). These light wave guides in the steel tube are surrounded by a gel.
Now electro-optical cables and overhead wires are known, in which a plurality of small LWG tubes (diameter about 2.5 mm) are no longer positioned in one of the wire layers about the core, but the core itself is formed as a comparatively larger LWG tube (diameter about 5 mm).
In German Published Application Patent DE 34 46 766 A1 (BBC) Electro-optical overhead wire with about 4 light wave guides is described. This overhead wire has the following structure from the furthest interior radially to the exterior: a plastic filling material; 4 LWG (coated optical fibers); a tube made from fibre glass or carbon fibre reinforced plastic (FRP or CRP), diameter about 5 mm; a first layer of steel wires and a second and third layer of aluminum wires. The invention here relates primarily to the LWG tube, which is made from FRP or CRP.
German Published Patent Application 38 04 419 A1 (Siemens) describes an electro-optical overhead wire with greater than 15 light wave guides (LWG). This overhead wire has the following structure from the furthest interior radially to the exterior: LWG-core bundle with about 15 LWG embedded in cross-linked silicon; a tube in the form of three nonmetal sheaths; a first layer of steel wire and two layers of aluminum wire. The invention here relates primarily to the LWG tube in the form of three nonmetal layers.
In European Published Patent Application 0 371 660 A1 (Stamnitz) an electro-optical undersea cable is described with more than 24 LWG. This undersea cable has the following structure from the furthest interior radially to the exterior: Up to 24 LWG loosely embedded in gel; high quality steel tube; about 1.25 mm in diameter with a wall thickness of about 0.125 mm; a layer of electrically conductive material-wire, in which several wires are replaced by a high quality steel pipe with several (about 3) LWG; extruded dielectric and 2 layers of steel wire as reinforcement. The invention relates here to an undersea cable structure which has more than 24 light wave guides.
In addition electro-optical cables and overhead wires are also known in which the light wave guides are disposed around a comparatively large core element, which has a comparatively large diameter of about 5 mm or more and acts as a high tension and supporting element. These references are as follows:
In German Published Patent Application 36 21 158 A1 (Philips) an electro-optical overhead wire having 6 light wave guides is described. In a first cable structure one FRP (fibre glass reinforced plastic) supporting element is surrounded with 6 coated light wave guides. A filling mass of silicon rubber or ethylene propylene rubber is provided. The surrounding tube is made from aluminum profile wires followed by a layer of aluminum alloy (E-AlMgSi) round wires and aluminum clad steel (ACS) round wires. The invention in this reference concerns the filling mass.
In German Published Patent Application 35 35 827 A1 (Fujikura) an electro-optical overhead wire with 36 light wave guides is described. This overhead wire has the following structure: a central element of steel wire with a FRP sheath; around this element 6 LWG cables with 6 LWG each; a soft filling material made from a plastic resin; a rigid filling material in form of a sleeve or tube made from plastic resin; a metal tube (Al, Cu, Fe) and a layer of conductive wire. Herein the LWG cables have the following detail structure: a core of steel or FRP wire; around this 6 LWG each loosely positioned in a sheath; a soft filling material and then a rigid tube. In this reference the invention concerns primarily the nature of the filling material and also the structure of the electro-optical cable.